This invention relates to on-off loading and dumping linkages for load receiving bodies carried on a truck frame.
U.S. Pat. No. 5,108,247, issued Apr. 28, 1992, entitled xe2x80x9cLoading Linkagexe2x80x9d and assigned to the same assignee as the instant application, the entire disclosure of which is herein incorporated by reference, discloses a loading linkage that is multi-functional and which is intended to be mounted on the frame of a dumpster hauling truck. The linkage provides for on loading or off loading the dumpster to the truck frame as well as a dumping mode wherein the contents of the dumpster may be dumped while still attached to the truck. This linkage has been in commercial use for a goodly number of years and has been very successful in the applications for which it is intended. The linkage includes a secondary link and a tilt link pivoted to the frame and which extend under and up the front of a dumpster on the truck. A dump link is also provided and extends under the dumpster and is pivoted to the rear of the truck frame. A first power cylinder pivotally engages the secondary link for tilting the secondary link relative to the truck frame and a second power cylinder is provided for pivoting the tilt link relative to the secondary link.
The tilt link, adjacent the dump link, has a locking tab that underlies a similar tab on the dump link in one position so as to lock all of the links for movement in unison under power from the first cylinder to effectuate a dumping mode. In addition, the tilt link may be tilted relative to the secondary link under the power of the second power cylinder to remove the tab from a position underlying the dump link to disconnect the dump link from the remaining links, thus allowing movement of the tilt and secondary links without movement of the dump link under power from the first cylinder to effectuate the on-off loading mode.
Typically, the tilt link has a hook at its end remote from the secondary link which is engageable with a grab bar mounted on the front wall of the dumpster. The hook, when engaged with the grab bar, provides the necessary engagement with the dumpster to provide on-off loading of the dumpster on the truck as well as to hold the dumpster in place during the dumping mode.
Proper operation of the linkage requires that when on loading a dumpster, the operator should totally retract the first power cylinder before retracting the second power cylinder. If this order of operation is not followed and the second power cylinder is retracted before the first power cylinder, the tilt tab and dump tab at the interface of the tilt link and the dump link may not properly align with the tab on the tilt link coming down on top of the tab on the dump link, rather than underlying the same as is intended. The result may cause damage to the tilt or secondary links.
The present invention is directed to obviating the possibility of such damage when linkage is improperly operated.
It is the principal object of the invention to provide an improved multi-function linkage for use on a truck that may be operated in an on-off loading mode for loading or unloading a dumpster on the truck and which may additionally be operated in a dumping mode for dumping the contents of a dumpster while the dumpster is secured to the truck. More specifically, it is an object of the invention to provide such a linkage wherein the possibility of damage to one or more links of the system is obviated even when the linkage is improperly operated.
In one exemplary embodiment, the invention contemplates a truck frame of a dumpster hauling truck that provides on-off loading and dumping modes which includes a dump link pivoted to the truck frame, a secondary link pivoted to the dump link and a tilt link pivoted to the secondary link to extend under and up the front of a dumpster. A first extendable dump motor is provided for pivoting the secondary link relative to the truck frame and a second extendable motor is provided for pivoting the tilt link relative to the secondary link. Interengageable tabs, one on the tilt link and one on the dump link, are provided to connect all of the links for movement in unison under power from the first extendable motor to effectuate the dumping mode. The invention contemplates the improvement wherein one of the tabs is pivotally and slidably mounted to one of the tilt and dump links and further includes an element normally connecting the one tab to one of the tilt and dump links to normally hold the one tab against the pivotal and slidable movement when the one tab is subjected to excessive force.
In a preferred embodiment, the connecting element is a frangible element.
In a preferred embodiment, the frangible element is a breakaway bolt connecting the one tab to the one of the secondary and dump links.
A preferred embodiment contemplates the provision of a pivot pin connecting the one tab to the one of the tilt and dump links and that the frangible bolt be spaced from the pivot pin.
In a highly preferred embodiment, the one tab, at a location remote from the other tab, includes an elongated opening of greater size than the pivot pin and the pivot pin extends through the elongated opening.
Even more preferably, the elongated opening is defined by a tube fixed to the one tab at the aforementioned location.
In a highly preferred embodiment, the tube is of generally rectangular cross section and even more preferably, the one tab is mounted to the dump link.